The invention relates to a method for thermally conditioning a prober that serves to check and test electronic components at defined temperatures. The invention also relates to a prober to execute the thermal conditioning.
A prober is defined hereinafter as a test device that measures the electrical functions of electronic components. A prober is used for checking or testing a wide variety of electronic components in various production stages. For example, these components can be semiconductor components in the wafer composite or individual components, like semiconductor chips, hybrid components, micro-mechanical or optical components or the like, for which reason the electronic components that are to be tested shall be referred to hereinafter as simply the test substrate.
A test substrate of this type generally exhibits a smooth and planar underside and is arranged and held, at least indirectly, on a chuck, which is an essential part of the prober and has a smooth and planar receiving surface for receiving the test substrate. The test substrate can be displaced with the chuck in the working area by means of a chuck drive, so that it can be positioned in relation to the test probes of the prober. The positioning of the test substrate is generally effected in the horizontal plane—that is, the X-Y plane—by means of a cross table as well as by means of a device for an angular orientation in a range of a few degrees and by means of a vertical—that is, Z lift—that makes possible, for example, an infeed movement of the test substrate in the direction of the test probes that are arranged above the test substrate.
Moreover, the holders of the test probes also exhibit their own positioning device, with which, for example, a plurality of test probes can be oriented relative to each other or to a preferential direction of the test substrate in the X, Y and Z direction, or an infeed movement to the test substrate can be effected.
For testing purposes the test probes, which have the form of contacting needles, make contact with the test substrate, to which test signals are applied or from which test signals are picked off. The test signals can vary widely. For example, the output signals can be generated by other input variables, such as radiation in a number of wavelength ranges, for example. The test probes are generally located outside the working area on the upper closure of the housing and make contact with the test substrate through an aperture in the housing.
The operational reliability of electronic components is tested in probers preferably under the environmental conditions that correspond to the conditions of use of the component in question. In this context the setting of the test substrate to defined temperatures is a main focus. The temperature of the test substrate is set by way of the chuck that can be heated or cooled by means of suitable devices.
In order to set the test conditions, the working area of the prober is generally surrounded by a housing. Such a prober surrounded by a housing is known from DE 4109908 C2. In this prober the housing exhibits a plurality of inlet openings in the lower section and an additional opening that serves as both an outlet opening and to provide the test probes access in the upper closure of the housing. When testing in the lower temperature range, a gas flow is provided through the working area by means of these openings, in order to prevent the precipitation of moisture from the surrounding atmosphere on the test substrate.
In order to reach the temperature, at which the test substrate is supposed to be tested, a suitable coolant is applied to the chuck. In order to adjust the temperature or to set even more controlled test conditions at the chuck, said chuck is connected to the corresponding sources, located outside the working area, by way of media lines. Whereas in this prober the chuck drive is also cooled as a result of the heat exchange with the chuck, DE 102 6 282 A1 describes a prober, in which the receiving surface of the chuck and the chuck drive are thermally almost decoupled, and the test substrate is shielded against the thermal radiation of the surrounding uncooled components by means of a directly cooled thermal radiation shield. In contrast to the former prober, the thermal separation could significantly reduce the amount of time and effort it takes to position the chuck with the accuracy and repeatability necessary for the test substrate, because the measuring time is significantly influenced by the onset of a thermal equilibrium in the measurement environment, and this environment was minimized. However, even in the case of the latter prober it was found that as the measuring time advances, the sequence of movements changes as a result of a progressive change in the thermal conditions of the positioning devices, thus adversely affecting to varying degrees the accuracy and repeatability of the test at different temperatures and different time lapses.